Motion picture cameras such as video cameras have been required to have a function to prevent vibration caused by camera shake, and various types of vibration-proof optical systems have been disclosed. For example, a zoom lens disclosed in JP-A-8-29737 includes an optical system consisting of two parts attached in front of the zoom lens in order to correct camera shake, where either of the parts is moved vertically to an optical axis in order to correct movement of images caused by camera shake.
A zoom lens disclosed in JP-A-7-128619 comprises four groups, where a part of the third lens group comprising plural lenses is moved vertically to the optical axis in order to correct the movement of images caused by camera shake.
However, the zoom lens disclosed in JP-A-8-29737 has an increased lens diameter for an optical system to correct camera shake for the purpose of attaching the optical system in front of the zoom lens. Accordingly, the entire component is upsized and a load on a driving system will be heavier. As a result, the zoom lens is unfavorable in view of downsizing, weight-reduction and power-saving.
The zoom lens disclosed in JP-A-7-128619 corrects image movement caused by camera shake by moving a part of the third lens group vertically to the optical axis while the same lens group is fixed with respect to the image plane. This type of zoom lens is more favorable than a zoom lens of front-attachment type in view of downsizing, but a load on the actuator will be heavier since the lens group for correcting camera shake is composed of three lenses.
Since an optical system for correcting camera shake is attached in front of the zoom lens disclosed in JP-A-8-29737, the lens diameter of the optical system will be increased, and the entire component will be upsized. So a load on the driving system will be heavier, and thus, this zoom lens is unfavorable in view of downsizing, weight reduction and power-saving.
The latter zoom lens in JP-A-7-128619 is advantageous in downsizing and weight reduction when compared to a type comprising an optical system for correcting camera shake in front of the zoom lens, since a third lens group is fixed with respect to the image plane and a part thereof is moved vertically with respect to the optical axis. However, the zoom lens has a problem of deterioration in aberration, especially for chromatic aberration, when shifting lenses, since a part of the third lens group is moved.